1. Field of the Invention
The present invention relates to a touch device, and in particular to a touch device in which a touch pad and a base are provided. A touch of conductive object on the touch pad and a relative movement between the touch pad and the base are all detected via the same capacitive sensors on the touch pad, so that it is unnecessary to provide force sensors and associated circuits to detect the movement.
2. Description of Prior Art
Touch device is provided with a pad on which a plurality of sensors is arranged, whereby contact behaviors of an object on the pad can be detected. There are many kinds of sensors, and capacitive sensors are used herein as an example for illustration. Such capacitive sensors are constituted of conductors and are connected to a controller for scanning the respective capacitances of the sensors. When an electrical conductive object approaches the pad, the capacitances of the sensors will be changed. By comparing the difference between the capacitances of the sensors in different positions, the region touched by the electrical conductive object can be determined. Thus, when using the capacitive touch device, the user only needs to use a conductive object 61 (such as his finger) to touch the pad for coordinates input, such as pressing keys or buttons to trigger the operation, or inputting pointing control signals.
Although the above-mentioned touch device can convert the sliding trajectory of the conductive object 61 into the output of the pointing control signals, it still cannot replace all functions of the traditional mouse such as left/right keys, scrolling roller, and dragging desired images or words by pressing the left key then moving the mouse. Thus, in addition to a traditional touch pad, two buttons adjacent to the touch pad have to be provided for operations of the left/right keys. Even though the user may operate the touch pad to trigger the control signals like the mouse via assistance of the two buttons, such a touch pad still cannot satisfy the operating habit of the user. On the other hand, for the user, operating the touch pad lacks a tactual feedback generated when pressing the keys.
The tactual feedback accompanied with pressing the keys not only conforms to the habit of the user as operating mechanical keys, but also provides the user with an informative signal related to the completion of pressing.
U.S. Pat. No. 5,854,625 discloses a force sensing touch pad, in which a sensor board and a plurality of spring structures are provided in a frame. The spring structures can support the relative movement of the sensor board respected to the frame. A plurality of capacitors is used to measure the distance between the sensor board and the frame. When the user tips the sensor board, only touch signals are outputted. When the user presses the sensor board, the plurality of capacitors will send a signal relating to the distance, thereby providing another force-operated signal.
Also, U.S. Patent Publication No. 2007/0262968 discloses an input device, which includes a capacitive touch pad, a data processor and a switch. When the capacitive touch pad is pressed, the switch is turned on, so that the data processor can output control signals different from those before pressing.
Thus, either the capacitor or electric switch is a force sensor that is provided outside a touch sensor to output force signals to a controller of the touch sensor. In this way, the controller can be switched to output different control signals and the functions of the touch pad can be expanded. For example, tipping the touch pad is one operating mode, and pressing the touch pad is another operating mode.
According to the above, no matter what kind of force sensors is used, the controller of the touch pad has to be additionally provided with an input port and operational circuits to process the force signals. In addition, in order to compare the touch signals with the force signals at the same time, the controller has to be provided with a synchronous clock circuit. To reduce the influence of electromagnetic waves on the original analysis circuits caused by the circuits associated with the force sensor, the whole dimension of the controller will be inevitably increased. Therefore, in order to process the force signals, additional elements such as operational circuits, the synchronous clock circuit, and electromagnetic wave protection circuit not only raise the cost in designing and developing integrated circuits (IC), but also increase the dimension of ICs and the basic cost of products.
In view of the above, it is an important issue for the present inventor to expand the input functions of the touch pad without providing an additional force detection circuit or modifying the analysis circuit for touch detection, whereby the production cost is reduced and the sensitivity of products is increased.